The present invention relates to apparatus or tools for gauging the openings of a workpiece, especially bulky workpieces which consist of sheet metal or the like. More particularly, the invention relates to improvements in apparatus for ascertaining the positions of openings in such workpieces.
It is frequently necessary to ascertain whether or not the opening in a workpiece is held in proper position for insertion of a screw, bolt, pintle, shaft, stud or the like. Such determination is particularly important when the part which is to be received in the opening is manipulated by an automatic tool which can insert the part only if the opening is maintained in a desired or optimum position with reference to the tool. In many instances, the openings are circular holes or bores, and it is then normally necessary that the axis of the hole or bore coincide exactly with the axis of the part which is to be inserted therein. The likelihood that the position of an opening will deviate from the anticipated or desired position when the workpiece which is formed with such opening assumes a position in which an automatic tool is to insert a part into the opening is particularly likely to arise if the workpiece consists of sheet metal which tends to undergo, and often undergoes, deformation in the course of a stamping, punching, profiling or analogous operation. For example, doors, hoods and other components of frames of motor vehicles are likely to be deformed during shaping so that the parts which serve to secure the components of the frame to each other are not likely to find their way into openings which are provided therefor. The actual position of an opening in a sheet-metal workpiece can deviate from the desired position in any one of practically infinite number of directions. In many instances, the deviation of the actual position from a desired or optimum position of the opening is not very pronounced; however, even a relatively slight deviation suffices to prevent an automatic tool from properly introducing parts into improperly positioned openings with the result that the workpiece and/or the part to be inserted is damaged or defaced and/or that the part simply cannot enter the opening. This can cause prolonged delays and losses in output when the workpieces are treated in a production line.